Identifying and Reducing Scaling Problems in Solar Hot Water Systems

Solar Energy ◽  
2002 ◽  
Author(s):  
Derek K. Baker ◽  
Gary C. Vliet
Keyword(s):  
Heat Exchanger ◽  
Potable Water ◽  
Hard Water ◽  
Water Systems ◽  
Hot Water ◽  
Tank Wall ◽  
Rate Model ◽  
Premature Failure ◽  
Water Side ◽  
Freeze Damage

In areas with hard water, scaling can reduce the reliability of solar hot water (SHW) systems. Common reliability problems associated with scaling are both mechanical (collector freeze damage, clogged passages, premature failure of pumps and valves) and thermal (efficiency degradation). A mechanistic and a mathematical scaling rate model are presented. Results from controlled experiments investigating the effect of key water chemistry and heat transfer parameters on the scaling rate are summarized. The implications of these results for designing SHW systems for scaling environments are discussed. Most importantly, indirect systems where the potable water side of the heat exchanger is integrated into the storage tank wall, such as in a wrap-around heat exchanger, are shown to be the most mechanically and thermally reliable systems for scaling environments. A new version of the software SolScale is discussed, which is intended to aid in the design of SHW systems to reduce scaling related reliability problems.

Identifying and Reducing Scaling Problems in Solar Hot Water Systems

2003 ◽  
Vol 125 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Derek K. Baker ◽  
Gary C. Vliet
Keyword(s):  
Heat Exchanger ◽  
Potable Water ◽  
Hard Water ◽  
Water Systems ◽  
Hot Water ◽  
Tank Wall ◽  
Rate Model ◽  
Premature Failure ◽  
Water Side ◽  
Freeze Damage

In areas with hard water, scaling can reduce the reliability of solar hot water (SHW) systems. Common reliability problems associated with scaling are both mechanical (collector freeze damage, clogged passages, premature failure of pumps and valves) and thermal (efficiency degradation). A mechanistic and a mathematical scaling rate model are presented. Results from controlled experiments investigating the affect of key water chemistry and heat transfer parameters on the scaling rate are summarized. The implications of these results for designing SHW systems for scaling environments are discussed. Most importantly, indirect systems where the potable water side of the heat exchanger is integrated into the storage tank wall, such as in a wrap-around heat exchanger, are shown to be the most mechanically and thermally reliable systems for scaling environments. A new version of the software SolScale is discussed, which is intended to aid in the design of SHW systems to reduce scaling related reliability problems.

Designing Solar Hot Water Systems for Scaling Environments

2000 ◽  
Vol 123 (1) ◽  
pp. 43-47 ◽  
Author(s):  
Derek Baker ◽  
Gary Vliet
Keyword(s):  
Heat Exchanger ◽  
System Reliability ◽  
System Performance ◽  
Potable Water ◽  
Hard Water ◽  
Performance Degradation ◽  
Hot Water ◽  
Tank Wall ◽  
Water Side ◽  
Component Failures

Component failures and system performance degradation in SHW systems due to scaling are common in areas with hard water. It appears that many valve and pump failures on the potable water side are related to scaling, and any scale build-up on heat transfer surfaces will result in performance degradation. Different designs are compared in regard to their susceptibility to problematic scaling. Indirect systems utilizing external and tank wall heat exchangers are compared in regard to the rate of scaling and the consequences of scaling on system performance. The tank wall heat exchanger appears preferable over a doubly pumped external heat exchanger, both in terms of system reliability and resistance to performance degradation.

scholarly journals Introduction of Monochloramine into a Municipal Water System: Impact on Colonization of Buildings by Legionella spp

2006 ◽  
Vol 72 (1) ◽  
pp. 378-383 ◽  
Author(s):  
Matthew R. Moore ◽  
Marsha Pryor ◽  
Barry Fields ◽  
Claressa Lucas ◽  
Maureen Phelan ◽  
...  
Keyword(s):  
Potable Water ◽  
Sampling Site ◽  
Water System ◽  
Water Source ◽  
Water Systems ◽  
Hot Water ◽  
County Government ◽  
Single Family ◽  
Pinellas County ◽  
Municipal Water

ABSTRACT Legionnaires' disease (LD) outbreaks are often traced to colonized potable water systems. We collected water samples from potable water systems of 96 buildings in Pinellas County, Florida, between January and April 2002, during a time when chlorine was the primary residual disinfectant, and from the same buildings between June and September 2002, immediately after monochloramine was introduced into the municipal water system. Samples were cultured for legionellae and amoebae using standard methods. We determined predictors of Legionella colonization of individual buildings and of individual sampling sites. During the chlorine phase, 19 (19.8%) buildings were colonized with legionellae in at least one sampling site. During the monochloramine phase, six (6.2%) buildings were colonized. In the chlorine phase, predictors of Legionella colonization included water source (source B compared to all others, adjusted odds ratio [aOR], 6.7; 95% confidence interval [CI], 2.0 to 23) and the presence of a system with continuously circulating hot water (aOR, 9.8; 95% CI, 1.9 to 51). In the monochloramine phase, there were no predictors of individual building colonization, although we observed a trend toward greater effectiveness of monochloramine in hotels and single-family homes than in county government buildings. The presence of amoebae predicted Legionella colonization at individual sampling sites in both phases (OR ranged from 15 to 46, depending on the phase and sampling site). The routine introduction of monochloramine into a municipal drinking water system appears to have reduced colonization by Legionella spp. in buildings served by the system. Monochloramine may hold promise as community-wide intervention for the prevention of LD.

scholarly journals Isolation ofMycobacterium aviumfrom Potable Water in Homes and Institutions of Patients with HIV Infection in Finland and the United States

2015 ◽  
Vol 2015 ◽  
pp. 1-3 ◽  
Author(s):  
Matti Ristola ◽  
Robert D. Arbeit ◽  
C. Fordham von Reyn ◽  
C. Robert Horsburgh
Keyword(s):  
United States ◽  
Hiv Infection ◽  
Potable Water ◽  
Nontuberculous Mycobacteria ◽  
The United States ◽  
Common Species ◽  
Water Systems ◽  
Human Infection ◽  
Hot Water ◽  
Symptomatic Disease

Symptomatic disease by nontuberculous mycobacteria has been linked to potable water from institutional and domestic potable water systems. Potable water samples were collected from homes and institutions of patients with AIDS. Colonization of potable water with nontuberculous mycobacteria was demonstrated in 230 (15%) of 1489 samples collected from domestic and institutional water systems of patients with HIV infection in the United States and Finland.Mycobacterium aviumwas the most common species and colonization was favored at temperatures of 40–50°C in recirculating hot water systems. Such systems are a plausible source of human infection and disease.

Characterization of a Thermosyphon Heat Exchanger for Solar Domestic Hot Water Systems

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Cynthia A. Cruickshank ◽  
Stephen J. Harrison
Keyword(s):  
Heat Exchanger ◽  
Test Procedure ◽  
Water Systems ◽  
Climatic Conditions ◽  
Hot Water ◽  
Test Method ◽  
Domestic Hot Water ◽  
Operational Conditions ◽  
Flow And Heat Transfer

This paper presents a simplified test method that was developed to allow preconfigured solar domestic hot water systems that use natural convection/thermosyphon heat exchangers to be characterized. The results of this test method produce performance coefficients for simple empirical expressions that describe the fluid flow and heat transfer in the heat-exchange loop. These empirically derived coefficients can be used as an input to a general simulation routine that allows overall system performance to be determined for various loads and climatic conditions. To illustrate the test procedure, results are presented for a typical heat exchanger under a range of operational conditions.

scholarly journals Heat Exchanger Design and System Balance of an Air Source Heat Pump/Chiller Using Brazed Plate Heat Exchangers

1997 ◽  
Author(s):  
Changiz Tolouee
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Hot Water ◽  
Pump Efficiency ◽  
Plate Heat ◽  
Air Source Heat Pump ◽  
Water Side ◽  
Brazed Plate Heat Exchangers

Air Source heat pump/chiller is used to provide chilled water for cooling and hot water for heating purposes. This is one investment for both applications with no requirement for boiler and fuel with the advantage of heat pump efficiency. In this paper we are going to analyse both air side and water side heat exchangers used in air source heat pump/chiller with special attention and emphasis on brazed plate heat exchanger which is used in refrigerant to water side of this unit in order to achieve optimum performance in both the heat pump and chiller operations. Due to compactness of brazed plate heat exchangers it is very important to balance system volume in both operating conditions which will also be examined in this paper.

Sporadic Legionnaires' disease: the role of domestic electric hot-water tanks

2011 ◽  
Vol 140 (1) ◽  
pp. 172-181 ◽  
Author(s):  
S. F. DUFRESNE ◽  
M. C. LOCAS ◽  
A. DUCHESNE ◽  
C. RESTIERI ◽  
J. ISMAÏL ◽  
...  
Keyword(s):  
Potable Water ◽  
Water System ◽  
Water Systems ◽  
Pulsed Field Gel Electrophoresis ◽  
Hot Water ◽  
Clinical Isolates ◽  
Domestic Hot Water ◽  
Legionnaires Disease ◽  
Water Tanks

SUMMARYSporadic community-acquired legionellosis (SCAL) can be acquired through contaminated aerosols from residential potable water. Electricity-dependent hot-water tanks are widely used in the province of Quebec (Canada) and have been shown to be frequently contaminated withLegionellaspp. We prospectively investigated the homes of culture-proven SCAL patients from Quebec in order to establish the proportion of patients whose domestic potable hot-water system was contaminated with the sameLegionellaisolate that caused their pneumonia. Water samples were collected in each patient's home. Environmental and clinical isolates were compared using pulsed-field gel electrophoresis. Thirty-six patients were enrolled into the study.Legionellawas recovered in 12/36 (33%) homes. The residential and clinical isolates were found to be microbiologically related in 5/36 (14%) patients. Contaminated electricity-heated domestic hot-water systems contribute to the acquisition of SCAL. The proportion is similar to previous reports, but may be underestimated.

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